Apparatus for vacuum crystallization



Aug. 3, 1937- M. J. KERMER 2,088,601

AFPARATUS FOR VACUUM CRYSTALLIZATION Filed July 29, 1952 3'Sheets-Sheet 1 20 vac 50,001 v. k. vapor650 rfi I! I, d 1m 20 1/ a.

IN VEN TOR A TTORNEYS Patented Aug. 3, 1937 APPARATUS FOR YIACU'UM CRYSTALLIZA- ION Martin J. Kermer, Buffalo, N. Y., assignor to Buffalo Foundry & Machine Company, Buffalo, N. Y., a corporation of New, York Application July 29, 1932, Serial No. 626,179

3 Claims.

This invention relates to an improved method of vacuum crystallization and apparatus therefor.

In crystallizing apparatus as heretofore constructed each of the several effects of the apparatus was equipped with its own condenser and steam ejector or pump which were wholly independent of the corresponding equipment of the other efiects which is objectionable on account of the large quantities of cooling water required in to operate under the necessarily high vacuums.

In many such installations the cooling water is above the temperature of the vapor of the last stage and in such cases it was necessary and it has been a common practice to compress this 15 vapor to a higher pressure so as to make it possible to use the available water for condensing purposes. Owing to the last stage being normally under an extremely high vacuum the com- 'pressionof this vapor had to be done in a num- 20 ber of stages which involved the use of additional apparatus and also consumed an undue amount of steam.

One of the objects of this invention is to reduce to a minimum the amount of steam and water used in creating the vacuums in the various stages of the operation of the apparatus.

Another object of this invention is to more ei'ficiently separate the salts that are crystallized during these stages from the mother liquor so 30 that when the liquor is returned to the apparatus for further cooling, it remains in touch with the colder liquor and thus gives the crystals a better opportunity to grow.

A further object of this invention is to so or- 35 ganize the apparatus that in its method of operation it is possible to continuously draw liquor and vapors from one stage to another without interrupting the operation of the apparatus.

In the accompanying drawings:

Figure 1 is a diagrammatic representation of one form of apparatus embodying my invention and carrying out my improved method of crystallization under vacuum. a

Figure 2 is a similar view of a modified form of .15 an apparatus constructed in accordance with my improvement.

Figure 3 is another view of the same character showing a further variation of this invention.

In the following description similar characters 50 of reference indicate like parts in the several views of the drawings.

Referring to Fig. 1, the numerals A, B, C represent a plurality of crystal or salt precipitators forming part of the first, second and third units, respectively, of the means forming the successive ing chambers H), II, l2 respectively, each of which is formed with a hollow body provided with an upright cylindrical sidewall l3, a downwardly tapering conical bottom It, and an upwardly dished top l5. The bottom is provided at its lower end with a crystal outlet l6 which is controlled by a Valve I1, and above the top is arranged a liquid outlet dome I8 which communicates at its lower end with the upper end of the respective precipitating chamber and is provided on its opposite sides with two liquid outlets I9, 20 .the former for use in re-circulating some of the liquid in the same unit and the latter for transferring some of the liquid from the respective unit to another unit.

Above the several precipitators is arranged a series of separators D, E, F associated, respectively, with the first, second and third effects, for separating the liquid .and vapors which are discharged into the precipitators preparatory to taking out the crystals or salts from the liquid and condensing some of the vapors and utilizing the heat in the uncondensable vapors for heating purposes in another unit. One of these separators forms an element in the unit of each effect and each separator comprises a separating chamber formed within a hollow body having an upright cylindrical side wall 2|, a downwardly tapering conical bottom 22, an upwardly dished top 23, a liquid inlet 24 in its side, a liquid outlet pipe 25 extending fromthe lower end of its bottom downwardly through the dome of the respective precipitator and terminating at its lower end in the central part of the precipitating chamber, and a. vapor outlet 26 arranged at the upper end of the separating chamber. Circulation of some of the crystal laden liquor within the same unit is efiected by a unit return pump 21 having its inlet connected by a pipe 28 with the outlet IQ of the companion dome l8 while the outlet of this pump is connected with the liquor inlet 24 of the companion separating chamber by a pipe 29.

' Each of the separators is provided between the upper and lower ends of the body forming its chamber with an inlet 30 for the salt solution, and in the unit of the first efiect this inlet is .connected with a supply pipe 3| whereby the original mother liquor is supplied to the apparatus, and in the second and third effects the inlet 30 in each instance is connected by a transfer pipe 32 with the transfer outlet 20 of the dome of preceding effect. The original supply pipe 3| and the transfer pipes 32 are each provided with a valve 33 for controlling the flow of mother liquor through 5 the same.

Each of the separators is provided on its inner side with a depending deflector 34 which directs the vapors and liquid issuing from the respective circulating pipe 29 downwardly toward the bottom of the respective separating chamber. Within the separating chamber between the deflector 34 and the vapor outlet 26 of this chamber is arranged a bail'ie device for eliminating from the vapors any liquid entrained therein which device in its preferred form comprises a plurality of inclined baflle plates 35 which are arranged in a vertical series and extend alternately inwardly from opposite sides of the wall of the separating chamber so that the vapor in passing from the lower edge of the deflector 34 to the vapor outlet 25 will be compelled to take a tortuous path and thus cause liquid entrained in the vapor to be deposited on the underside of the baffle plates and fiow from the latter to the lower part of the separating chamber where it joins the unvaporized liquid and is delivered with the same into the precipitator arranged underneath.

The operation of the precipitator and separator in the unit of each effect is as follows:

It will be assumed that the mother liquor is delivered in a heated condition into each separator through the inlets 30, that the pumps 21 are running and that an exhausting device serves to create a vacuum in each unit so as'to withdraw the vapors through the vapor outlets 26 of the several separating chambers. Under these conditions the crystal laden liquor or salt solution will pass from the lower end of each separating chamber through the respective delivery pipe 40 25 into the precipitating chamber below. As the crystal laden liquor enters the precipitating chamber part of the crystals therein will drop to the bottom of this chamber from where they are removed upon opening the valve l1 while the 4.5 liquid containing more or less crystals passes from the lower end of the pipe 25 upwardly in the precipitating chamber to the dome thereof. Some of this liquor is withdrawn by the pump 21 from the dome and carried back to the same 50 separating chamber for the purpose of further separating vapors therefrom in the separating chamber and also further eliminating crystals therefrom in the precipitating chamber.

Some of the mother liquor is also withdrawn 55 by vacuum through the transfer pipe 32 and carried over into the separating chamber of the unit in the next following effect. Any vapor' separated 'from the liquor as it enters the separating chamber through the original inlet 30 and 0 the return inlet 24 is carried off by vacuum through the vapor outlet 26 of the separator.

The several effects of this apparatus include means for condensing the condensable vapors which are withdrawn from the separators, also 05 means for creating a vacuum in the apparatus and causing the vapors to be carried away from the separators to the condensers. The condensers for the units of the first, second and third effects are designated G, H, I and each of these con- 70 densers comprises a condensing chamber formed within a hollow body having an upright side wall 33, a downwardly tapering conical bottom I 31, an upwardly dished top 33, a water inlet 39 near its top, a water outlet 4|! at its bottom, a 75 vapor outlet 4| at its top, a vapor inlet 42 near its bottom. and a plurality of catch basins 43 arranged in staggered relation within the condensing chamber. Water is supplied to the uppermost basin of the condenser of the unit constituting the third effect by a pipe 44 containing a controlling valve 45, and from this uppermost basin the water flows in the form of cascades successively to each lower basin and finally escapes through the water outlet at the bottom of the condensing chamber. From each condensing chamber of the third and second effects the water is carried by a transfer pipe 46 to water inlet 39 of the next preceding condensing chamber and each of these transfer pipes is provided with a depressed trap 41, the water in which forms a seal to prevent any one of these condensing chambers venting into the other.

The water outlet 40 of the condenser of the first effect connects with the upper end of a discharge pipe 48 which has its lower end immersed in water contained in a trap tank 49, thereby forming with the condensing chamber of the first effect a barometric condenser which creates a vacuum in the chambers connected with the upper end of the pipe 48 due to a falling column of water therein, which water may be discharged from the tank 49 into a sewer or elsewhere as desired.

The vapor is conducted from the vapor outlet 26 ofthe separating chamber of the third effect C to the vapor inlet 39 of the condensing chamber of the third effect by a vapor transfer pipe 50 containing a comparatively large steam operated ejector 5| whereby the vapor is forcibly carried away from this separator and a vacuum is created in the latter and other parts of the apparatus' communicating therewith.

The vapor outlet 26 at the upper end of the separating chamber E of the second effect is connected by a vapor transfer pipe 52 with the vapor inlet 42 of the companion condensing chamber H and the separating chamber D of the first effect has its vapor outlet 26 also connected by a pipe 53 with the vapor inlet 42 of the companion condensing chamber.

Means are provided for withdrawing non-condensable vapors from the upper end of each condensing chamber to thereby create a vacuum therein. This is preferably effected by connecting a comparatively small steam actuated ejector 54 with the vapor outlet 4| of each condensing chamber. The outlet of the ejector 54 of the third effect is connected by a vapor pipe 55 with the vapor transfer pipe 52 leading from the separating chamber E to the condensing chamber H of the second effect, the outlet of the vapor ejector 54 of the second effect is connected by a pipe 56 with the pipe 53 leading from the separating chamber D to the condensing chamber G of the first effect, and. the outlet of the vapor ejector 54 of the condensing chamber G of the first effect leads by a pipe 51 to the atmosphere.

As the vapors pass from the vapor inlet 42 to the vapor outlet 4| thereof the same pass through the cascades of water and more or less of the condensable vapors therein are liquefied and the resulting condensate mixes with the condensing water from the pipe 44 and flows to the inlet 39 of the condensing chamber of the second effect. In the condensing chamber of the second eifect the vapors from the separating chamber E' of the second effect discharged by the pipe 52 and the vapors carried from the condensing chamber of the third effect by the pipe 55 are passed through the streams of water in the condensing chamber of the second eifect, thereby causing further liquefaction of the condensable gases or vapors, which condensate joins the water passing from the condensing chamber of the second effect to the condensing chamber of the first eflect.

The vapors withdrawn from the condensing chamber H of the second effect and the vapors discharged from the separating chamber of the first effect are carried by the pipes 55, 53 to the lower end of the condensing chamber of the first effect, and thence pass upwardly through the sprays or streams of water therein, whereby any of the vapors which are condensable will be liquefied and descend with the water into the pipe 48 and pass on the sewer.

Any uncondensable vapors which pass through the streams of the water in the condensing chamber G are merely ejected through the pipe 51 as waste. The mother liquor leaving through the outlet 20 of the dome of the third stage at its lowest temperaturecan be further treated either by evaporation or other means or returned to the system for further precipitation, for which purpose the liquor may be withdrawn from said outlet 20 by a pump 58 connected therewith by a pipe 59.

The operation of the apparatus as a whole is as follows:-

Live steam is supplied to the main ejector 5| at the rate of 950 pounds per hour, and to each of the auxiliary ejectors 54 at the rate of pounds per hour equivalent to 125 pounds gage pressure. The mother liquor is supplied by the supply pipe 3| at a temperature of 210 F., and this temperature drops successively to 161 F., 105 F. and 59 F. as the mother liquor in turn enters the separators of the first, second and third effects. The steam supplied to the ejector 5| withdraws the vapors from the separator F at the rate of 650 pounds per hour producing a vacuum of 29 inches .of vacuum in this separator with the barometer at 30 inches, and this vapor added to the 950 pounds of steam supplied to the ejector 5| makes a total of 1600 pounds of vapor entering the condenser I of the third effect.

In this condenser a temperature of 101 F. and a vacuum of 28 inches is maintained by the supply of water atnormal temperature of approximately F. and 157 gallons per hour and the supply of steam to the ejector 54 of the third condenser at the rate of 70 pounds per hour. The condensation of the steam supplied to the ejector 5| added to the water supplied by the pipe 44 produces a total of approximately 160 gallons per minute which is delivered to the condenser H of the second effect at a temperature of 96 E, which volume of water is finally discharged from the sump or tank 49 of the barometric condenser of the first effect. v

In the condenser H and the separator E of the second effect a vacuum of 27 inches is produced by the ejector 54 connected with the condenser H of the second efiect, and vapor is withdrawn by this ejector from this unit at the rate of approximately 670 pounds per hour. The non-condensable vapors withdrawn by the ejector 54 from the condenser l. of the third effect are compressed to a pressure equivalent to that maintained in the condenser H, the mixed vapors being conducted from the ejector 54 of condenser I by a pipe 55 to the condenser H.

The steam supplied to the ejector 54 of the first efiect produces a vacuum of 20 inches in the con- 75 denser G and the separator D of this eflect and results in the production of 720 pounds of vapor per hour in this-unit, during which operation the uncondensable gases or vapors which are withdrawn from the condenser H of the second effect to the condenser I of the third eflect are conducted by the pipe 56 to the separator and condenser of the first eflect.

The sum of the non-condensable gases is finally discharged through the pipe 51 to the atmosphere, and the final mother liquor is discharged tl'iifrough the outlet 20 of the dome ID of the third e ect.

As the cooling water passes through the condenser I the same has been raised in temperature from 75 F. to approximately 96 F. and has also been raised in quantity from 157 g. p. m. to 160 g. p. 111. due to the addition thereto of condensa tion of vapors in the condenser I.

As the cooling water flows from the condenser H of the second efiect to the condenser G of the first efiect its temperature has been raised to F., and when the condensate escapes from the pipe 48 of the condenser G of the first effect its firgiperature has been raised to approximately During the operation of the apparatus shown in Fig. 1, as described the temperatures of the liquid in the precipitators F, E, and D are approximately 75 F., F. and 1'73 F., respectively, while the temperature of the vapors in these precipitators is approximately 59 F., 105 F. and 161 F., respectively. In this apparatus a comparatively large amount of steam is initially used for compressing the vapors withdrawn from the separator F and delivered to the condenser I of the third eifect and only comparatively small amounts of steam are required for removing the non-condensable gases from the condensers of each effect and delivering the same to the condenser of the preceding effect for raising the temperature of the vapors in the latter. A very considerable economy in the use of steam and water is thus effected for extracting the crystallizable salts in a certain quantity of mother liquor compared with the methods and apparatus heretofore known or used.

The construction and operation of the modifled form of the apparatus shown in Fig. 2 is as follows:-

In this apparatus three effects or stages are employed in which the precipitators A, B, C, the separators D, E, F and the liquor transferring and re-circulating means are substantially like those shown in Fig. 1 and the description and reference characters hereinbefore employed in connection with Fig. 1 therefore also apply to the corresponding parts shown in Fig. 2. In Fig. 2 the transfer pipes 32 containing the valves 33 connect the domes N3 of the first and second effect with the tops of the precipitating chambers ill of the second and third effects, respectively.

In this modified form of the apparatus comparatively large steam actuated ejectors 60, 6| are connected respectively with the upper ends of the separating chambers E, F of the second and third effects and a single barometric condenser J is employed for disposing of the condensate ofthe several units and assisting in the formation of a vacuum in the separating chambers of the several efiects. The ejector 6| receives steam through a pipe 62 for withdrawing vapor'from the upper end of the separator F of the third eflect and discharges the same through a pipe 63 into the upper end of the separator E 'of the second effect. Theejector I8 is operated by steam supplied by a pipe 88 for withdrawing vapor from the upper end of the separator E of the second effect and discharges the same by a pipe 65 into a coupling 66 which communicates with the upper end of the separator D of the first eifect. The pipe 65 and coupling 66 are connected by a pipe 61 with the lower part of the body J 01 the condenser, which latter is constructed like the condenser G of the first effect in Fig. 1, and is provided adjacent to its upper end with a water supply pipe 88 having a controlling valve 89 while its top connects with a comparatively small ejector l supplied with steam by a pipe H and its bottom is connected with a barometric discharge or stand pipe 12 leading to a trap tank 18 similar to the tank 48 in Fig. 1.

In this organization the vapors from the separator F in the third stage are removed from the ejector 8| and discharged into the upper part of the separator E of the second stage. The vapors formed in the separator E of the second stage plus the vapors from the separator F of the third stage are now withdrawn by the ejector 68 and in turn discharged into the condenser J together with the vapors drawn from the condenser D of the first stage, the exhausting efiect on the vapors in the last-mentioned condenser being produced by the action of the barometric condenser J. All of the uncondensable gases in the vapors in this apparatus are drawn off from the top of the condenser body J and discharged to the atmosphere.

Assuming that the fresh mother liquor is supplied through the pipe 3l at a temperature of 210 F., condensing water through the pipe 08 at a temperature of 75 F. and that steam is supplied to the several ejectors 60, 8i and 10 at 125 pounds gage pressure, the temperature of the solutions in the separators F, E, D of the third, second and first stages will be approximately 75 F., 125 F. and 175 F. respectively; the temperature of the liquid in the stand pipe 12 will be about 150 F.: the temperature of the vapors in the separators F, E, D of the third, second and first stages will be about 59 F., 109 F. and 159 F. respectively, and the vacuum in the separators F, E, D of the third, second and first stages will .be approxi-' mately 29.5 inches, 27.5 inches and 20 inches respectively.

The further modified form of apparatus containing this invention and shown in Fig. 3 is constructed as follows:-

In this construction theprecipitators A, B, C and the separators D, E, F of the first, second and third stages or effects are also similar to those shown in Fig. 1 and the previous description of the construction and operation of the same parts therefore applies to both. An important difference between the forms shown in Figs. 1 and 3 is that in Fig. 3 only the separator F of the third effect is provided with an ejector II which is actuated by steam from a pipe 15 and the body K of a barometric condenser is connected by pipes l6, l1 and a coupling 18 with the outlet of the ejector II and the vapor outlet at the top of the separator D, and an individual condenser is provided for the second stage, the body L of which is connected with the vapor outlet at the top of the separator E by an outlet pipe 19. The condenser bodies K, L are provided with individual water supply pipes .80, 8| for condensing Purposes, also with water discharge pipes 82, 83 leading to the trap tanks 84, 85, and also with individual steam actuated electors 81, 88 for withdrawing the uncondensable gases from the condensers K, L and discharging the same to the atmosphere.

In Fig. 3 the mother liquor-is conducted directly by the pipe 8| into precipitating chamber I. of the first effect, and this liquid is transferred by the pipes 32 containing the valves 33 from the domes i8 of the precipitators of the first and second effect to the precipitating chambers Ill of the second and third effects, respectively.

Assuming that water at a temperature of 75 F. is supplied through the pipes 80, 8| to the condensers, that steam at 125 pounds gage pressure is supplied to the ejectors H, 85 and 81 and that the mother liquor is supplied through the pipe 8i at a temperature of 210 F., this will result in a temperature of 59 F., a vacuum of 29.5 inches and formation of 650 pounds of vapor per hour in separator F of the third stage, a temperature of 109 F., a vacuum of 27.5 inches and the formation of 670 pounds vapor per hour in the separator E of the second stage, and a temperature of 159 F., a vacuum of 20 inches and the formation of 710 pounds of vapor per hour in the separator D of the first effect, while the temperature of the condensate escaping from the condensers K, L will be respectively 150 F. and 100 F.

A feature common to all the several forms of this invention is that non-condensable gases are removed from the separator body of one stage and blown into the separator body of a preceding stage for the purpose of using as little steam as possible for ejecting or compressing the vapors.

The construction in Fig. 2 further differs from that shown in Fig. 1 in that the latter employs individual condensers G, H, I for the vapors in the several stages, while in the former the vapors are carried from the separators D, E, F of the several stages to a single condenser J.

The construction shown in Fig. 3 further differs from that shown in Fig. 1 in that the former employs one condenser K which is common to the separators D, F of the first and third stages, and an individual condenser L is employed for use with the separator E of the second stage.

In addition to effecting a considerable saving in heat and water, this apparatus produces a circulation of the liquor through the apparatus so as to cause a uniform cooling of the entire mass of solution which is subjected to the process of crystallization.

I claim as my invention:-

1. An apparatus for crystallizing salts in a solution, comprising a plurality ofeffects each of which includes a separating chamber in which vapors are separated from the mother liquor and which has a downwardly projecting outlet, a wide settling chamber into which said outlet projects and in which salt crystals are separated from the mother liquor, and a narrow outlet chamber which receives mother liquor from the central upper part of the settling chamber, liquor conduits each connecting the narrow outlet chamber of each preceding effect with the separating chamber of the next following eifect, a condensing means associated with each of the separating chambers, means for supplying cooling water to each of said condensing means, steam operated ejecting means for withdrawing vapors from the separating chamber of the last efiect and discharging the same to the condensing means of the same effect, and steam operated ejecting means for withdrawing vapors from the condensing means of successively to the several condensing means of the preceding efiects and to the atmosphere.

2. An apparatus for crystallizing salts in a solution comprising a plurality of eflects each which includes a separating chamber in which.

' vapors are separated from the mother liquor,

and which has a downwardly projecting outlet, a wide settling chamber into which said outlet projects and in which saltcrystals are separated from the liquor, a narrow outlet chamber which receives liquor from the central upper part ofthe settling chamber, a liquor conduit connecting the narrow outlet chamber of each preceding effect with the separating chamber of the next succeeding effect, a condensing chamber associated with each of said vapor separating-chambets, means for supplying condensing water successively to the condensing chambers of the several effects including a water conduit connectin the lower part of the condensing chamber of each succeeding effect with the upper part'oi the condensing chamber of the respective preceding effect and containing a water seal which prevents the passage of vapor through the same from one of thesecondensing chambers to the other. a

steam operated ejector having its inlet connected with the upper part of the separating chamber of the last eflect and its outlet connected with the condensing chamber '01 the respective eflect, a steam operated ejector having its inlet connected with the condensing chamber 0! the last effect and its outlet connected with the condensing chamber of the next preceding effect, ,a steam operated ejector having its inlet connected with the condensing chamber of the first eflect and its outlet leading to the atmosphere, and a vapor conduit connecting the upper part of each preceding separating chamber with the lower part of the condensing chamber of the corresponding 3. An apparatus for crystallizing salts in a solution comprising a plurality of effects each 0! which includes a separating chamber in which vapors are separated from the mother liquor and which has a downwardly projecting outlet, a wide settling chamber into which said outlet projects and in which salt crystals are separated from the liquor, a narrow outlet chamber which receives liquor from the central upper part of the settling chamber, a pump ch withdraws liquor from said narrow outlet chamberand discharges the same into the respective separating chamber, a liquor conduit connecting the narrow outlet chamber of each preceding effect with the sepa- "rating chamber of the next succeeding effect, a condensing chamber associated with each 01 said vapor separating chambers, means for supplying condensing water successively to thecondensing chambers of the several effects including a water conduit connecting the lower part of the condensing chamber of each succeeding effect with the upper part of the condensing chamber of the respective preceding effect and containing a water seal which prevents the passage of vapor through the same from one of these condensing chambers to the other, a steam operated ejector having its inlet connected with the upper part c! the separating chamber of the last eflect and its outlet connected with the condensing chamber 'of therespective eflect, a steam operated ejector having its inlet connected with the condensing chamber of the last eflect and its outlet connected with the condensing chamber of the next preceding effect, a steam operated ejector having its inlet connected with the condensin! chamber of the first effect and its outletleading to the atmosphere, and a vapor conduit connecting the upper part of each preceding separating chamber with the lower part 01 the condensing chamber of the corresponding effect.

I MARTIN J. 

